1. Field of the Invention
The present invention relates to an ink jet recording apparatus, and more particularly to an ink jet recording apparatus for recording images in a recording medium having an ink absorbability such as paper or fabric.
2. Description of Related Art
As an image recording apparatus capable of recording images not only in a normal recording medium such as paper or fabric but also a recording medium of low ink absorbability such as a resin film or a metal, an ink jet recording apparatus that jets an ink from a nozzle disposed in one end surface of a recording head so that the ink lands on the recording medium has been developed, and this technique is applied in various technical fields at present. Among them, a photocurable ink jet recording apparatus that applies light such as ultraviolet rays to the ink landed on the recording medium so as to harden and fix the ink has actively been developed as a recording apparatus which enables easy acquisition of high-definition images (e.g., Japanese Patent Application Laid-Open No. 2004-188864 and Japanese Patent Application Laid-Open No. Hei 6-200204).
As such an ink jet recording apparatus, in Japanese Patent Application Laid-Open No. 2004-188864, the applicant of the present invention discloses a technique of an ink jet recording apparatus which includes a plurality of ultraviolet-ray sources different in a peak wavelength of emitted light as main sensitivity wavelengths of inks of various colors such as yellow (Y), magenta (M), cyan (C) and black (K) jetted from a recording head vary from ink to ink. Especially it is disclosed an ink-jet apparatus where an ultraviolet-ray source having a shorter peak wavelength of emitted light is positioned closer to the recording head, so that ultraviolet rays of longer wavelengths is applied after application of an ultraviolet ray of a shorter wavelength to the ink landed on the recording medium.
The ink jet recoding apparatus described in Japanese Patent Application Laid-Open No. 2004-188864 is useful especially when an image is recorded in a recording medium of low ink absorbability. In other words, the ink landed on a surface of the recording medium is irradiated with a short-wavelength ultraviolet ray to harden the surface, and then a long-wavelength ultraviolet ray is applied to harden the inside. Thus, blotting of the ink on the surface of the recording medium or color mixing such as mixing with an adjacent ink is prevented to enable acquisition of an extremely high-definition image.
However, when this method is applied to a recording medium having a high ink absorbability such as plain paper or fabric not treated for blotting prevention, so-called print through in which the ink soaks in the recording medium causing ink blotting or the ink to reach the backside of the recording medium may occur. Particularly, when a high-density image is formed, as the amount of ink putted in per unit area of the recording medium is increased, the ink blotting becomes more sever so as to increase a level of the print through.
According to the ink jet recording apparatus described in Japanese Patent Application Laid-Open No. Hei 6-200204, it is proposed that a thermally meltable ink containing wax, a resin and an ultraviolet curable resin having melting points at 40 to 70° C. is jetted to the recording medium, and the ink is hardened by applying ultraviolet rays while preventing ink blotting by the wax or the like.
According to these methods, however, ink blending, storage management, jet control or the like is complex and burdensome, and besides resistance to abrasion of the ink hardened on the recording medium, i.e., abrasion resistance, may be reduced to cause image quality deterioration.